CALLISTO | Black Tungsten Ring Two Yellow GroovesBlack Tungsten Ring Two Yellow Grooves 8MM This Ring is made of high grade tungsten carbide which provides excellent durability. Domed Black Tungsten Ring with Two Yellow Grooves of the Ring. Ring Measures 8mm in width for Men. Tungsten carbide rings are extremely durable and won't scratch or fade. This Ring is made of high grade tungsten carbide which provides excellent durability. It is cobalt free and offers resistance to scratching to keep its